Leakage detector for a sealed housing

ABSTRACT

To test the integrity of waterproof cases for cameras and like apparatus to be used underwater, a casing with a detector is provided. The air inside the casing is pressurized and the detector indicates leakage based on the difference between the pressurized air and atmospheric pressure. A decrease in pressure of the initial level of pressurized air implies leakage.

[0001] This application is a continuation-in-part of internationalapplication number PCT CA99/00122, filed Feb. 9, 1999 which is acontinuation-in-part of U.S. patent application Ser. No. 08/819,339(issued as U.S. Pat. No. 5,870,632).

FIELD OF THE INVENTION

[0002] This invention relates to the detection of leakage in a casingbased on sensing changes in the air pressure.

BACKGROUND OF INVENTION

[0003] Airtight or waterproof cases are used to enclose cameras andother sensitive apparatus to protect them from their operatingenvironment external to the case (herein “environment”), which may havemoisture, dust, gases and other harmful elements. Cases may suffer frommanufacturing defects and may consequently leak.

[0004] Detection of leaks in supposedly waterproof cases has beenconventionally attempted by detecting the presence of moisture. Schwomma(U.S. Pat. No. 4,312,580) is a representative example. Not only aremoisture detectors difficult and expensive to build and maintain, thedetection of moisture comes often too late (e.g. moisture has alreadyentered the casing).

[0005] As well, detection of leaks has been conventionally attempted byobserving changes in the air pressure inside the casing afterartificially increasing it. Hayakawa (U.S. Pat. No. 5,305,031) is arepresentative example. One defect of such attempts is that the meansfor increasing the air pressure and detecting changes, is itself apotential source of leakage in addition to possible leakage in thecasing. For example, after using the Hayakawa device to test theintegrity of the casing, it is neither clear that the “self-closing”seal will maintain its integrity nor how to test for that post-testingintegrity. Takamura (U.S. Pat. No. 4,763,145) and Prager (DE 38 37 624)are further examples wherein differential pressure of sub-chambers isused to detect leaks, however not all of such sub-chambers are incommunication with the environment.

SUMMARY OF THE INVENTION

[0006] To address the above defects with the conventional approaches,this invention provides a case comprising: (a) sealed housing with anouter wall; and (b) a leakage detector firmly located in said wallhaving: (i) a chamber with first and secondsub-chambers; (ii) first portmeans by which said first sub-chamber communicates with the environment;(iii) second port means by which said second sub-chamber communicateswith the environment; (iv) a partition separating said first sub-chamberfrom said second sub-chamber which moves in response to the differencein the respective air pressures of said first and second sub-chamber;and (v) indicator means, located proximate said partition and responsiveto movement of said partition, for indicating leakage.

[0007] To address the above defects with the conventional approaches,this invention provides a leakage detector for a sealed housing with anouter wall, comprising: (i) a chamber with first and secondsub-chambers; (ii) first port means by which said first sub-chambercommunicates with the environment; (iii) second port means by which saidsecond sub-chamber communicates with the environment; (iv) a partitionseparating said first sub-chamber from said second sub-chamber whichmoves in response to the difference in the respective air pressures ofsaid first and second sub-chamber; and (v) indicator means, locatedproximate said partition and responsive to movement of said partition,for indicating leakage.

[0008] To address the above defects with the conventional approaches,this invention provides a method of detecting leakage in a case,comprising the steps of: (a) creating a first sub-chamber of pressurizedair in communication with the interior of the case; (b) creating asecond sub-chamber of air; (c) abutting a portion of said firstsub-chamber with a portion of said second sub-chamber where the abutmentis in the form of a membrane whose profile changes in response to therelative differences in air pressures of said first and secondsub-chambers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Advantages of the present invention will become apparent from thefollowing detailed description taken in conjunction with preferredembodiments shown in the accompanying drawings, in which:

[0010]FIG. 1 is a rear perspective view of an underwater camera housingemploying a leakage detector according to the present invention;

[0011]FIG. 2 is a perspective view of the leakage detector according tothe present invention;

[0012]FIG. 3(a) is a top view of the detector of FIG. 2;

[0013]FIG. 3(b) is a side view of the detector of FIG. 3(a) taken alongline II-II therein;

[0014]FIG. 4(a) is a top view of the injector head of the presentinvention;

[0015]FIG. 4(b) is a side view of the injector head of FIG. 4(a) takenalong line II-II therein;

[0016]FIG. 5(a) is a top view of the plug of the present invention;

[0017]FIG. 5(b) is a side view of the plug of FIG. 5(a) taken along lineII-II therein;

[0018]FIG. 6 is a side view of the injector head inserted into thedetector according to another embodiment;

[0019]FIG. 7 is a side view of the plug inserted into the detector;

[0020]FIG. 8 is a perspective view of the leakage detector according tothe present invention;

[0021]FIG. 9(a) is a top view of the detector of FIG. 8;

[0022]FIG. 9(b) is a side view of the detector of FIG. 9(a) taken alongline II-II therein;

[0023]FIG. 10(a) is a top view of the injector head of the presentinvention;

[0024]FIG. 10(b) is a side view of the injector head of FIG. 10(a) takenalong line II-II therein;

[0025]FIG. 11(a) is a top view of the plug of the present invention;

[0026]FIG. 11 (b) is a side view of the plug of FIG. 11(a) taken alongline II-II therein;

[0027]FIG. 12 is a side view of the injector head inserted into thedetector;

[0028]FIG. 13 is a side view of the plug inserted into the detector;

[0029]FIGS. 14a to 14 f are side and top views of an alternativeembodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030]FIG. 1 shows underwater camera housing 10, which has front part 10a and rear part 10 b held together by several spring-loaded latches(one, 10 c, is shown in FIG. 1). Silicon or rubber O-ring 10 d providesa waterproof seal between front and rear parts 10 a and 10 b whenlatched together. Leakage detector 20 is connected to housing 10 at hole15 in rear part 10 b (explained below). Leakage detector 20 has severalpurposes, in addition to detecting leakage. To pressurize the air inhousing 10, plastic hand or finger pump 99, is employable with leakagedetector 20 through injector head 40. Leakage detector 20 is pluggedwith plug 50.

[0031] As shown in FIGS. 2 and 3, detector 20 has a convex, annularupper body 21 with a central port 23 to receive injector head 40 or plug50 (explained below), and a hollow stem 22 depending downwardly. Stem 22and hole 15 are respectively profiled to create a tight friction fitwhen stem 22 is inserted in hole 15 and the connection is conventionallysealed with glue, O-rings and ultrasonically bonded. The base of body 21is profiled to hug rear part 10 b in a flush manner. Body 21 has threesockets 27 which interact with corresponding wings 28 of injector head40 or plug 50 (explained below) to create a tight interlock therewith.Within body 21 is elastic membrane 25 (explained below) and the portionof body 21 proximate membrane 25 is transparent and has a visible scaleof graduations 26 to permit viewing of the profile of membrane 25relative thereto (as shown in FIG. 2).

[0032] Body 21 has atmospheric sub-chamber 30, in the shape of a partialtorus, in communication with the environment by sub-chamber port 31 anddetector central port 23. Body 21 has pressurized sub-chamber 32, in theshape of a partial torus, in communication with the interior of housing10 through stem 22. Detector central port 23 communicates withsub-chamber 32 by a one-way valve 24. Atmospheric sub-chamber 30 isseparated from pressurized sub-chamber 32 by flexible membrane 25. Asthe air pressure in sub-chamber 32 increases above atmospheric pressure,the profile of membrane 25 will change. From an initial flat profile,membrane 25 will curve or bulge inwardly into atmospheric sub-chamber30. The profile of membrane 25, and in particular the crown of a bulgedprofile, is visible to the user through the transparent portion of body21 relative to graduations 26 thereon. One particular graduation maysignify the appropriate pressure for testing particular housing 10.Generally, the graduations are usable as visual markers and the exactsignificance of any particular graduation can be determined by the userbased on the particular housing being tested.

[0033] Injector head 40, as shown in FIG. 4, has O-ring 41 and threeequi-spaced wings 28 which interact with corresponding sockets 27 ofdetector 20 for a bayonet or similar type secured interlock withdetector central port 23.

[0034] Plug 50, as shown in FIG. 5, has a bottom protuberance 51, upperO-ring 42 and lower O-ring 43, and three equi-spaced wings 28 whichinteract with corresponding sockets 27 of detector 20 for a bayonet orsimilar type interlock with detector central port 23. Upper O-ring 42and lower O-ring 43 are disposed on plug 50 such that when plug 50 isinserted and secured in detector central port 23, upper O-ring 42 andlower O-ring 43 bracket sub-chamber port 31. Protuberance 51 is locatedon plug 50 so that when plug 50 is inserted and secured in detectorcentral 23, protuberance 51 pushes down and thereby opens valve 24 topermit air from pressurized sub-chamber 32 to enter detector centralport 23.

[0035] Plug 50 also has a gripping means 55, which may be a coin slot orplastic handle which the user may easily manipulate to insert and securethe wing-socket interlock mentioned above.

[0036] As shown in FIG. 6, the user drills a hole in housing 10 rearpart 10 b with a suitable profile to accept stem 22 of detector 20 in atight friction fit (and sealed as described above); inserts detector 20and then inserts injector head 40 into detector central port 23. O-ring41 is disposed below sub-chamber port 31 so that atmospheric sub-chamber30 is in direct communication with the environment. By user manipulationof pump 99, air is forced through valve 24, into sub-chamber 32 and theninto the interior of housing 10. The resulting increased air pressurewill tend to create a curved profile of membrane 25 and the extent ofcurve will be visible to the user relative to graduations 26. The userwill stop pressurizing at a suitable pressure level (after consideringthe movement of membrane 25 relative to graduations 26, membrane 25 willhave its initial profile), withdraw injector head 40, and insert andinsert and secure plug 50 in detector central port 23, as shown in FIG.7. The user will observe if membrane 25 changes its initial curvedprofile. If there is leakage in housing 10, the air pressure inpressurized sub-chamber 32 will decrease and the curved profile willflatten. A suitable period to observe for changes depends on factorslike the confidence level sought by the user.

[0037] The opening of valve 24 by protuberance 51 (as explained above)allows pressurized air from pressurized sub-chamber 32 to move into thetiny cracks between plug 50 and proximate portions of detector centralport 23 which are circumscribed from above by lower O-ring 43. If theseal created by lower O-ring 43 leaks, air will escape throughsub-chamber port 31 into atmospheric sub-chamber 30. The result will bea decrease in pressure in sub-chamber 32 and a corresponding change inprofile of membrane 25 can be detected by the user. In such a condition,even if the seal of upper O-ring 42 was sufficient to prevent leakage, achange in the profile of membrane 25 would be interpreted as a warningto the user to consider replacing plug 50 because lower O-ring 43 hadfailed. Also, although atmospheric sub-chamber 30 is typically incommunication with the atmosphere during testing for leakage, theoperating environment of detector 20 in housing 10 typically has hostileelements and therefore, atmospheric sub-chamber 30 is advantageouslysealed therefrom by upper O-ring 42.

[0038] Thus it is seen that beyond naturally doubling the integrity ofthe seal of plug 50, having a pair of O-rings 42 and 43 configured asdescribed above, provides additional benefits.

[0039] The profile of membrane 25 that indicates the absence of leakage(i.e. the constancy of the profile from the initial curve of membrane25) will be present only if there is no leakage in housing 10 and noleakage in detector 20. Upon detection of leakage, suitable correctiveaction can be taken. For example, during the quality checking process asthe last step in the manufacture of housings, a particular housing 10which leaked can be rejected or returned for correction. Aftersuccessful manufacture and testing (e.g. while it is stored in inventoryor being transported), housing 10 equipped with detector 20 providescontinuous detection of leakage, whether of housing 10 or plug 50.

[0040] For example, housing 10 for a camera may be dimensioned 6″×4″×2″and made of polycarbonate. Detector 20 may be dimensioned 1″ in diameterand body may be 2″ in height and made mainly of polycarbonate.

[0041] Sub-chamber 30 may be a part toroidal-shaped cylinder with oneend closed and the other end open. Sub-chamber 32 may be similarlyconstructed. Sub-chambers 30 and 32 are joined at their open ends andseparated by membrane 25, which may a sheet of elastic material coveringone open end and sealed conventionally. Membrane 25 may be made of suchelastic material and dimensions, and secured in place, as areappropriate for the particular application but in any case, membrane 25must be sufficiently strong to provide an air tight separation betweensub-chambers 30 and 32 even while being sufficiently flexible to bulgewithout undue air pressure. For example, membrane 25 may be latex rubberor silicon sheet which is bracketed conventionally over the open end ofpressurized sub-chamber 32. Membrane 25 and its connection should beable to withstand pressure up to 8 psi for testing housing 10 for atypical camera.

[0042] Valve 24 may be a conventional silicon or rubber one-way valvebut biasing on springs or other conventional means are possible as longas the self-closing sealing action is quick.

[0043] A second embodiment of the invention, as shown in FIGS. 8-13, isvery similar to the first embodiment shown in FIGS. 1-7. In FIGS. 8-13,reference numerals which are identical to those in FIGS. 1-7 representsimilar or identical elements.

[0044] In contrast to the first embodiment, in the second embodiment,atmospheric sub-chamber 30 is separated from pressurized sub-chamber 32by oil drop 125. In effect, the indication of leakage created by themovement of flexible membrane 25 in the first embodiment is replacedwith the indication of leakage created by the movement of oil drop 125within transparent tube 126 which is itself disposed within a proximate,transparent portion of body 21 to permit viewing of the location of oildrop 125. Tube 1 26 is conventional and is at most 1 millimeter indiameter. Oil drop 125 is conventional industrial oil (as can beobtained from suppliers like Texaco) having attributes of low viscosity,non-vaporizing, and surface cohesion appropriate for the detection of apressure leak according to this invention.

[0045] Injector head 140 is the same as injector head 40 but has anadditional cross bars 28 a at the bottom thereof, as shown in FIG. 10.

[0046] Plug 150 (unlike plug 50 as shown in FIG. 5) has no bottomprotuberance.

[0047] Valve 124 (unlike valve 24 as shown in FIGS. 3,6,7), is aconventional one-way valve, spring biased into the closed postion. Valveabutment 124 a protrudes above the floor of central port 23 in closedposition. Valve 124 is opened by the downward pressing against valveabutment 124 a by cross-bars 28 a of injector head 140 (as shown in FIG.12) or by plug 150 (as shown in FIG. 13).

[0048] Valve 124 may be a conventional silicon or rubber one-way valvebiased in the closed position by quickly acting springs. Otherconventional means are possible as long as the self-closing sealingaction is quick.

[0049] In a third embodiment, as shown in FIGS. 14a to 14 f, instead ofusing pump 99 to force air into sub-chamber 32, pump 99 is used towithdraw air from sub-chamber 32. In this embodiment membrane 25 willchange its curved profile in the opposite direction as in the case whereair is forced into sub-chamber 32. As shown in the FIGS. 14a to 14 f, aspring loaded valve 61 is used that is biased in the closed position.Such a valve 61 is useful for either when air is pumped into sub-chamber32 or when air is withdrawn from sub-chamber 32.

[0050] Alternative means of displaying pressure differences betweensub-chambers 30, 32 include an LED display coupled with a pressuresensor or a spring loaded bellows.

[0051] It will be appreciated that the dimensions given are merely forpurposes of illustration and are not limiting in any way. The specificdimensions given may be varied in practising this invention, dependingon the specific application.

What is claimed is
 1. A case comprising: (a) sealed housing (10) with anouter wall; and (b) a leakage detector (20) firmly located in said wallhaving: (i) a chamber with first and second sub-chambers (30, 32); (ii)first port means (31) by which said first sub-chamber (30) communicateswith the environment; (iii) second port means (23) by which said secondsub-chamber communicates with the environment; (iv) a partition (25)separating said first sub-chamber from said second sub-chamber whichmoves in response to the difference in the respective air pressures ofsaid first and second sub-chamber (30, 32); and (v) indicator means(26), located proximate said partition and responsive to movement ofsaid partition, for indicating leakage.
 2. The case of claim 1, whereinsaid partition (25) includes a flexible membrane.
 3. The case of claim1, wherein said detector (20) has a transparent portion so that saidpartition movement is visible to a user.
 4. The case of claim 1, whereinsaid second port means (23) has a self-closing, unidirectional valve(24) which mediates between said second sub-chamber (32) and theenvironment in response to pressure directed into said secondsub-chamber (32).
 5. The case of claim 1 further comprising injectionmeans (40) for injecting air from the environment through said secondport means (23) and into said second sub-chamber (32) to increase theair pressure therein.
 6. The case of claim 2 further comprisinginjection means (40) for injecting air from the environment through saidsecond port means (23) and into said second sub-chamber (32) to increasethe air pressure therein.
 7. The case of claim 3 further comprisinginjection means (40) for injecting air from the environment through saidsecond port means (23) and into said second sub-chamber (32) to increasethe air pressure therein.
 8. The case of claim 4 further comprisinginjection means (40) for injecting air from the environment through saidsecond port means (23) and said valve (24) into said second sub-chamber(32) to increase the air pressure therein.
 9. The case of claim 1,wherein said detector (20) further comprises a plug (50) insertable intoand securable to said second port means (23) which, when secured,creates a seal between the environment and said second sub-chamber (32).10. The case of claim 2, wherein said detector (20) further comprises aplug (50) insertable into and securable to said second port means (23)which, when secured, creates a seal between the environment and saidsecond sub-chamber (32).
 11. The case of claim 3, wherein said detector(20) further comprises a plug (50) insertable into and securable to saidsecond port means (23) which, when secured, creates a seal between theenvironment and said second sub-chamber (32).
 12. The case of claim 4,wherein said detector (20) further comprises a plug (50) insertable intoand securable to said second port means (23) which, when secured,creates a seal between the environment and said second sub-chamber (32).13. The case of claim 9, wherein said plug (50) is configured to opensaid valve (24) to release air from said second sub-chamber (32) whensaid plug (50) is secured to said second port means (23).
 14. The caseof claim 10, wherein said plug (50) is configured to open said valve(24) to release air from said second sub-chamber (32) when said plug(50) is secured to said second port means (23).
 15. The case of claim11, wherein said plug (50) is configured to open said valve (24) torelease air from said second sub-chamber (32) when said plug (50) issecured to said second port means (23).
 16. The case of claim 12,wherein said plug (50) is configured to open said valve (24) to releaseair from said second sub-chamber (32) when said plug (50) is secured tosaid second port means (23).
 17. The case of claim 16, wherein said plug(50) has first sealing means (42) and second sealing means (43) which,when secured to said second port means (23), (i) bracket said first portmeans (31) so as to prevent leakage between said first sub-chamber (30)and the environment, and (ii) seal said second sub-chamber (32) fromsaid first sub-chamber (30) and the environment.
 18. A leakage detector(20) for a sealed housing (10) with an outer wall, comprising: (i) achamber with first and second sub-chambers (30, 32); (ii) first portmeans (31) by which said first sub-chamber (30) communicates with theenvironment; (iii) second port means (23) by which said secondsub-chamber (32) communicates with the environment; (iv) a partition(25) separating said first sub-chamber (30) from said second sub-chamber(32) which moves in response to the difference in the respective airpressures of said first and second sub-chamber (30, 32); and (v)indicator means (26), located proximate said partition (125) andresponsive to movement of said partition (25), for indicating leakage.19. The detector of claim 18, wherein said partition (125) includes aflexible membrane and the detector (20) has a portion proximate saidmembrane to permit a user to view movement of said membrane.
 20. Thedetector of claim 18, further comprising a transparent tube (126) whichconnects said first sub-chamber (30) from said second sub-chamber (32)and said partition includes an oil drop (125) disposed within said tube.21. A method of detecting leakage in a case, comprising the steps of:(a) creating a first sub-chamber (32) of pressurized air incommunication with the interior of the case; (b) creating a secondsub-chamber of air at atmospheric pressure (30); (c) wherein atransparent tube (126) connects said first sub-chamber (32) and saidsecond sub-chamber (30) and an oil drop (125) is disposed within saidtube (126), wherein said oil drop (125) moves in response to therelative differences in air pressures of said first and secondsub-chambers (32, 30).
 22. A method of detecting leakage in a case,comprising the steps of: (a) creating a first sub-chamber (30) incommunication with the environment; (b) creating a second sub-chamber(32) of pressurized air in communication with the interior of the caseand with the environment; (c) abutting a portion of said firstsub-chamber (30) with a portion of said second sub-chamber (32) wherethe abutment takes the form of a partition (25) which moves in responseto the difference in respective air pressures of said first and secondsub-chambers.